Eruption at Krafla, 1984

The Iceland hotspot is a hotspot which is partly responsible for the high volcanic activity which has formed the island of Iceland. Krafla is a Caldera of about 10 km in diameter with a 90 km long fissure zone in the north of Iceland in the Mývatn region Year 1984 ( MCMLXXXIV) was a Leap year starting on Sunday (link displays the 1984 Gregorian calendar) In Geology, a hotspot is a location on the Earth's surface that has experienced active volcanism for a long period of time Iceland, officially the Republic of Iceland ( ( Ísland or Lýðveldið Ísland (

Description

Iceland is one of the most active volcanic regions in the world, with eruptions occurring on average roughly every five years. Plate tectonics and hotspots Divergent plate boundaries At the About a third of the basaltic lavas erupted in recorded history have been produced by Icelandic eruptions. Basalt (bəˈsɔːlt ˈbeisɔːlt ˈbæsɔːlt is a common Extrusive Volcanic rock. Lava is molten rock expelled by a Volcano during an eruption When first expelled from a volcanic vent it is a Liquid at Temperatures Notable eruptions have included that of Eldgjá in 984 (the world's largest basaltic eruption ever witnessed), Laki in 1783 (the world's second largest), and several eruptions beneath ice caps, which have generated devastating glacial bursts, most recently in 1996. Eldgjá is a volcanic canyon in Iceland. Eldgjá and the nearby Laki craters are part of the same volcanic system as Katla in the south of the country Events By Place Asia Emperor Kazan succeeds Emperor En'yū on the throne of Japan. Laki or Lakagígar ( Craters of Laki) is a volcanic fissure situated in the south of Iceland, not far from the canyon of Eldgjá and Year 1783 ( MDCCLXXXIII) was a Common year starting on Wednesday (link will display the full calendar of the Gregorian calendar (or An ice cap is an Ice mass that covers less than 50 000 km² of land area (usually covering a highland area A glacial lake outburst flood (GLOF can occur when a lake contained by a glacier (called Jökulhlaup if it was a Subglacial lake, Marginal lake drainage Year 1996 ( MCMXCVI) was a Leap year starting on Monday (link will display full 1996 Gregorian calendar)

Iceland's location astride the Mid-Atlantic Ridge, where the Eurasian and North American Plates are moving apart, is partly responsible for this intense volcanic activity, but an additional cause is necessary to explain why Iceland is a substantial island while the rest of the ridge mostly consists of seamounts, with peaks below sea level. The Mid-Atlantic Ridge (MAR is a Mid-ocean ridge, a Divergent tectonic plate boundary located along the floor of the Atlantic Ocean. The Eurasian Plate is a Tectonic plate which includes most of the continent of Eurasia (a landmass consisting of the traditional Continents of Europe The North American Plate is a Tectonic plate covering most of North America, Greenland and part of Siberia. A seamount is a Mountain rising from the Ocean Seafloor that does not reach to the water's surface ( Sea level) and thus is not an Island Mean sea level (MSL is the average (mean height of the Sea, with reference to a suitable reference surface

As well as being a region of higher temperature than the surrounding mantle, it is also believed to have a higher concentration of water. The mantle is a part of an Astronomical object. The interior of the Earth, similar to the other Terrestrial planets, is Chemically divided Water is a common Chemical substance that is essential for the survival of all known forms of Life. The presence of water in magma reduces the melting temperature, and this may also play a role in enhancing Icelandic volcanism. Magma (Plurals magmas and magmata) is molten rock that sometimes forms beneath the surface of the Earth (or any other Terrestrial planet

Theories of causation

There is an ongoing discussion whether the hotspot is caused by a deep mantle plume or originates at a much shallower depth. A mantle plume is an upwelling of abnormally hot rock within the Earth's mantle. ^[1]

Some geologists have questioned whether the Iceland hotspot has the same origin as other hotspots such as the Hawaii hotspot. A geologist is a contributor to the Science of Geology, studying the physical structure and processes of the Earth and planets of the solar system The Hawaii hotspot is perhaps the best known volcanic hotspot on Earth, responsible for the Hawaiian Islands in the Pacific Ocean. While the Hawaiian island chain and the Emperor Seamounts show a clear time-progressive volcanic track caused by the movement of the Pacific Plate over the Hawaiian hotspot, no such track can be seen at Iceland. The Hawaiian-Emperor seamount chain is composed of the Hawaiian Ridge, consisting of the islands of the Hawaiian chain northwest to Kure Atoll, and the Emperor The Pacific Plate is an oceanic Tectonic plate beneath the Pacific Ocean.

Mantle plume theory

Main article: Iceland plume

It is believed that a mantle plume underlies Iceland, of which the hotspot is thought to be the surface expression. The Iceland Plume is an upwelling of anomalously hot rock in the Earth's mantle beneath Iceland whose origin probably lies at the boundary between the A mantle plume is an upwelling of abnormally hot rock within the Earth's mantle. This enhances the volcanism already caused by plate separation, both at the centre of the island and at the Reykjanes ridge to the southwest of Iceland's main volcanic zone. Reykjanes (pronounced /ˈreːkjəˌnɛs/) (or Reykjanesskagi) is a Peninsula and a volcanic system situated at the south-western end of Iceland The plume is believed to be quite narrow, perhaps 100 km across, and extends down to at least 400–650 km beneath the Earth's surface, and possibly down to the core-mantle boundary.

Studies suggest that the hotspot is only 50-100 K hotter than its surroundings, which may not be a great enough difference to drive a buoyant plume. The kelvin (symbol K) is a unit increment of Temperature and is one of the seven SI base units The Kelvin scale is a thermodynamic In Physics, buoyancy ( BrE IPA: /ˈbɔɪənsi/ is the upward Force on an object produced by the surrounding liquid or gas in which it is

It is suggested that the lack of a time-progressive track is because the plume may have been located beneath the thick Greenland craton for a significant time. A craton ( Greek kratos / κρἀτος ( neut. "strength" is an old and stable part of the Continental crust that has survived

See also

• Geography of Iceland
• Glaciers of Iceland
• Glacial lake outburst flood
• Iceland plume
• Lakes of Iceland
• List of islands off Iceland
• List of volcanoes in Iceland
• Plate tectonics
• Rivers of Iceland
• Volcanism in Iceland
• Waterfalls of Iceland

References

Further reading

• Allen, RM; Nolet, G; Morgan, WJ; et al. (1999). The thin hot plume beneath Iceland. Geophysical Journal International 137: 51-63.
• Foulger, GR; Anderson, DL (2005). Gillian Foulger is a Professor of Geophysics at Durham University. Don L Anderson (* 5 March, 1933, in Frederick, Maryland, USA is a US geophysicist who has made important contributions to the determination A cool model for the Iceland hotspot. Journal of Volcanology and Geothermal Research 141: 1-22.
• Nichols, ARL; Carroll, MR; Höskuldsson, Á (2002). Is the Iceland hot spot also wet? Evidence from the water contents of undegassed submarine and subglacial pillow basalts. Earth and Planetary Science Letters 202: 77-87.

External links

• http://www.mantleplumes.org/Iceland3.html